Snap acting thermal switch



April 15, 1941. E BLETZ 2,238,621

SNAP ACTING THERMAL SWITCH Filed Aug. 27, 1938 2 Sheets-Sheet 1 Fly: 1.

WITNESSES: INVENTOR I Edward Bletz.

ATTORNEY April 15, 1941. BLETZ 2,238,621

SNAP ACTING THERMAL SWITCH Filed Aug. 27, 1938 2 Sheets-Sheet 2 h fi 26' Fig.7. Fig. 8. Fig. 9. F1910.

fl Zb 15 0 9 16 36 o 90 Fly. 11 12a 22a m 400 m 3611 12a Fly .12. i B,

Fly '13. WITNESSES: 36a INVENTOR l Idward Bletz.

42 48 14a 24a BY 39a ATTORNEY Patented Apr. 15, 1941 SNAP ACTING THERMAL SWITCH Edward Bletz, Lexington, Ohio, assignor to West- Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylinghouse Electric &

vania Application August 27, 1938, Serial No. 227,043

Claims.

adjustable means for changing the curvature of.

the thermostatic element to afford means for adjusting the difierential of operation of the thermostatic switch.

A further object of my invention is to provide a rugged, eflicient, inexpensive, snap-acting switch which may or may not be adjustably operated after being assembled.

A still further object of my invention is to provide adjustable means for changing the curvature of the thermostatic element after being assembled.

Other objects of my invention will either be pointed out specifically in the course of the following description of a device embodying my invention, or will be apparent from such description.

In theaccompanying drawings,

Figures 1 and 2 are, respectively, side elevational views, partly in section, of a device embodying my invention in each of its two operating positions. r

Fig. 3 is a sectional view taken along the line IIIIII of Fig.1. v

Figs. 4 and 5 are a top plan view and a side elevational view, respectively, of the operating element and mounting device therefor.

Fig. 6 is a top plan view of the bimetallic operating element including in the structure shown in Figs. 5 and 6.

Figs. '7 and 8 are plan and side elevational views, respectively; of a member included in the mounting device shown in Figs. 4 and 5.

gs- 9 and 10 are plan and side elevational views, respectively, of an additional member shown in Figs. 5 and 6.

Fig. 11 is a perspective view of a modified form of the operating element shown in Fig. 6.

Fig. '12 is a top plan view of a'modified form of the structure shown in Fig. 4, illustrating means for changing the curvature of the thermostatic element, and

Fig. 13 is a sectional view taken along the line XIVXl.V in Fig. 12.

Referring to the accompanying drawings, I show a snap-acting, furcated, bimetallic thermal switch It) comprising a multi-furcated bimetallic operating element l2, an element support or mounting device 14 therefor, a main supporting structure or base l5, and a plurality of cooperating contacts I! and i9 operatively associated with the bimetallic element I2 and base l5, respectively.

The element support or mounting device M includes a top member I6, a base member I8 and a plurality of pins or studs 20 which cooperate with the top and base members and the bimetallic element l2.

The multi-furcated bimetallic operating element [2 is preferably formed or constructed from a single sheet of bimetallic material. However, it is to be understood that the element may be constructed in any other desirable manner. The element l2 comprises a plurality of exterior furcations 22 and at least one interior furcation 24, and an end portion 26. The iurcations 22 and 24 are preferably formed integral with the end portion 26 of the member l2. However, they may be rigidly attached thereto in any other desired manner. The'furcations 22 and 24 are substantially the same length and have slots or apertures 28 located therebetween. Small cir cular apertures 30 are positioned within the free ends' of the exterior furcations 22 and a similar aperture 32 is positioned within the free end of the interior furcation 24 somewhat closer to the end thereof than the apertures 30 position within the furcations 22, substantially as shown in Fig. 6. The apertures 30 and 32 cooperate with the element support or mounting device [4, which is adapted to maintain the interior furcation 24 in a curvature substantially opposite to that of the exterior iurcations 22, substantially as hereinafter described.

The bimetallic element i2 is rigidly attached, at one end thereof, to the element support I4,

, as hereinafter described, and has attached at its. free end the movable contact [1, which, in this instance, comprises an elongated bar 33 loosely attached to the element l2 by the ballheaded rivet 35, as shown in Figs. 1,2 and 3. The rivet 35 and bar 33 are insulated from element l2 by a suitable insulating grommet 31. However, it is to be understood the movable contact I! may be constructed and insulatedly attached to the element [12 in any desired manner.

The element support or mounting device M is, in this instance, formed from two main structural members; namely, a top member it and a bottom, member 68. The top member Mi is substantially a fiat metallic bar which has rigidly attached thereto a plurality of pins or studs positioned in substantially a straight line. These pinscooperate with and retain the operating element in a predescribed curvature, substantially as hereinafter described.

The base it includes a main portion 3 1 and an upwardly extending portion 3t, located at the rear end thereof. The upwardly extending portion 36 extends above the main portion M an amount substantially equal to the thickness of the multi-furcated bimetallic element 02. A plurality of apertures 38 are positioned within the main portion 34 to cooperate with the pins 2b in a manner substantially as hereinafter described, The support is then formed by having the top plate l5 positioned upon the upwardly extending portion 36 of the base [18 and rigidly attached thereto by means of suitable temporary assembly screws 40a.

The main supporting structure or base i5, shown in Figs. 1 and 2, comprises, in this instance, an elongated main-body portion 2i having a depending mounting portion 23 at one end thereof. However, it is to be understood that the supporting structure if may be formed in any other desired manner.

An adjusting device 3i, including a set-screw 25, is threadedly attached to the base I5, intermediate the ends thereof, by any suitable bushing 2l'. The set-screw has a reduced-diameter portion 29 located at the lower end thereof which cooperates with the central leg of the bimetallic element l2. This reduced-diameter portion 29 cooperates with the element H2 in such a manner that as the set-screw 25 is rotated there will be no binding action between the portion 29 and the element [2, In addition, the portion 29 fits the central leg of the element I2 so as to substantially prohibit any movement therebetween along the axis of set screw 25 as the element l2 flexes from one position to another. The adjusting screw 25 is then free to regulate the operation of the element [2 and thermostat iii.

The stationary contacts I9 are insulatedly connected to the free end of base l5, and comprise, in this instance, a contact portion 39 and a terminal portion M, which are, in this instance, threadedly engaged so as to be rigidly attached to the base I 5. Insulating grommets 23 are operatively associated with the contacts 89 to insulate them from the base it. However, it is to be understood that the contacts may be formed and mounted upon the base 05 in any desired manner so that they cooperate with the movable contact ii.

In assembling the operating element 82 and mounting device it, the multi-furcated bimetallic operating element (12 is positioned upon the base it of the support or mounting device i l and the top member in is positioned thereon. The pins or studs 2d operatively associated with the top member it then cooperates with the apertures til and 32 located within the free ends of the furcations 22 and 241, respectively, substantially as hereinafter described, and, in addition, with the apertures 3% located in the base it. The top member it is then rigidly attached-to the base it by means of the temporary assembling screws Mia or in any other suitable manner.

aasaoai When it is desired to mount the assembled operating element 02 and mounting device it upon the base it, the device it may be rigidly attached 7 to the depending portion 23 of such base, The 5 temporary assembling screws dim may be removed from the device it and replaced by screws which will cooperate with the base [5 and rigidly attach the device thereto. However, it is to be understood that the mounting device is and bimetallic operating element l2 may be attached to base H5 in any other suitable manner.

Inasmuch as the pins 20, operatively associated with mounting device M, are located in substantially a straight line, and inasmuch as the apertures 3d and 32, positioned within the free ends of the furcations 22 and 24, are not located in a straight line, when the pins 20 are inserted through the apertures 30 and 32, the free end of the intermediate furcation 24 will be forced inwardly causing such furcation to be curved with respect to the exterior furcations, say, upwardly, substantially as shown in Fig. 5. In addition, inasmuch as the intermediate furcation 24 is substantially the same length as the exterior furcaa tions 22, it follows that, when taking the device as a unit, as the free end of the intermediate furcation 24 is biased inwardly, due to the irregular position of aperture 32, located in the free end thereof, such furcation becomes in eiTect, between the points of support, longer than the exterior end portion 26 and exterior furcations 22 of member I2 comprise a frame for the thermostat which is attatched to the supporting structure M, the intermediate furcation 24 may then be construed as being a bridging member which. is longer than its supporting frame.

It is to be understood that, if desired, the apertures 30 and 32 may be located in a straight line with the intermediate pin 20 located closer to the edge. Accordingly, when the intermediate pin 20 cooperates with aperture 32, the intermediate furcation 24 may likewise be curved relatively upwardly substantially as hereinabove described.

The relative upward curvature of the intermediate furcation 24, together with its effective length being greater than that of the main element l2, causes the element !2 to havea similar curvature. However, it is apparent that such curvature thereof will be less than that" of the intermediate furcation 24, as shown in Fig. 2.

Duringoperation, as the thermostat and the bimetallic operating element 12 are subjected to an increase in temperature, the internal stresses of the element 52 are changed. Inasmuch as such member is formed. of bimetallic material, it will tend .to change its curvature or straighten itself and then reverse its curvature. By reason of the fact that the intermediate furcation is efiectively longer than the frame of member l2, the movement or reversal of curvature of such element results in a reversal of curvature of the intermediate furcation 2d and the entire operating element G2 with an abrupt or snap-action. V The movable contact ll positioned upon the free end of element is disengaged from the stationary contacts 19 by such snap-action, as shown in contact ill will then be reengaged with the stafurcations. In other words, assuming that the and the pins 20 positioned in an irregular line,

tionary contacts [9 with a snap-action, as shown in Fig. 1.

As the element l2 changes from one position to another, the intermediate furcation 24 figuratively passes through the element l2 from one side to the other. This action tends to cause a longitudinal stretching of the exterior furcations 22. The more readily these furcations stretch in response to temperature and then return to their original position, the more readily will the intermediate furcation change its position. Accordingly, it will be understood that the readiness with which such intermediate furcation 24 reverses its curvature determines the range of operation of the thermostat. That is, the more readily it operates, the smaller will be its range of operation.

It, therefore, follows that, if desired, the exterior furcations of the bimetallic element l2 may be formed in a sinusoidal or wavy manner substantially as shown by 22a of element 12a in Fig. 11. The wavy curvature of the exterior furcations 22a then permits such furcations to readily expand and contract longitudinally as the elements l2 flexes from one position to another, and, in turn, permits the thermostat to operate on a very small range or differential between its 011 and on positions.

As an important modified form of the mounting structure or device l4 shown in Figs. 4 and 5, the upwardly extending portion 36a of base Ma has a threaded aperture 48 located substantially at the midpoint thereof intermediate the screws a, as shown in Figs. 12 and 13. An adjusting screw 42 may then be threadedly engaged with the aperture so as to effect longitudinal engagement with the free end of the intermediate furcation 24a. The screw 42 may then be run in or out of or manually adjusted with respect to the base 14a so as to change the relative position of the free end of the intermediate furcation 24a, and to efiect changes in the curvature thereof. when using such a structure, the aperture 320, located in the free end of the furcation 24a, is slotted so as to permit free movement of the free end of the furcation 24a in response to the movement of the screw 42 (Fig. 13).

As the adjusting screw 42 is moved with respect to the base, the furcation 24a assumes corresponding changes in curvature; which, in turn, permits the thermostat to be readily adjusted to the desired operating differential after having been assembled. This feature is extremely important inasmuch as it permits the thermostat to be assembled and adjusted without the use of many expensive previously used tools and jigs.

Various other modifications may be made in the device embodying my invention without departing from. the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. In a circuit-controlling device, a member having a plurality of furcations of substantially equal length. a supporting structure therefor, and means comprising said structure for cooperatively simporting the free ends of said furcations, said furcations having lines of contact near one end with said structure and being retained in unalined formation by said structure to cause one of said furcations to become in eflect longerthan the others and to assume a curvature greater than that of the remaining furcations, projections of said furcations between said respective lines of contact and the other ends of the respective furcations on a plane parallel to the plane of an outer furcation being substantially equal.

2. In a circuit-controlling device, a multi-furcated bimetallic member, the furcations being of substantially equal length and the free end of one of them having an aperture initially unalined with apertures in the others, a supporting structure therefor, a plurality of substantially alined fastening means operatively associated with the structure, and means comprising said structure and fastening means for cooperatively supporting,

the free ends of said furcations, said furcations having lines of contact near one end with said support and being retained with said apertures in substantial alinement thereby to bow said one furcation relative to said others, projections of said furcations between said respective lines of contact and the other ends of the respective furcations on a plane parallel to the plane of an outer furcation being substantially equal. I

3. In a circuit-controlling device, a multi-iurcated bimetallic member, the furcations being of substantially equal length and the free end of a central one of them having an aperture initially unalined with apertures in the others, a supporting structure operatively associated with the free ends of the furcations including a base, a cover plate and a plurality of studs asociated therewith, said structure cooperatively supporting the rree. ends of the furcations, said furcations having lines of contact near one end with said sup-- port and being retained with said apertures in substantial alinement thereby to bow said one furcation relative to said others, projections of said furcations between said respective lines of contact and the other ends of the respective furcations on a plane parallel to the plane of an outer furcation being substantially equal.

4. In a circuit maker and breaker, a multi-furcated bimetallic member, said member having at least one interior iurcation, a supporting structure including a base, fastening means rigidly securing one end of the outer furcations and adjustably morning one end of said interior furcation to said base, said furcations having lines of contact near one end with said supporting structure, and adjusting means supported by the base and operatively associated with the adjustably secured end of the interior iurcation to vary the curvature of such furcation. projections of said furcations between said respective lines of contact and the other ends of the respective furcations on a plane parallel to the plane of an outer furcation being substantially equal.

5. In a circuit maker and breaker, a multifurcated bimetallic member, said member having at least one interior furcation, a supporting structure including a base, fastening means rigidly securing one end of the outer furcations and ada'ustably securing one end of said interior furcation to said base, said furcations having lines of contact with said base, and an adjusting screw threadedly engaging the base and operative longitudinally against the adiustabiy. secured end of the interior iurcation to increase or decrease the curvature of such iurcation, projections of said furcations between said respective lines of contact and the other ends of the respective furcations on a plane parallel to the plane'of an outer furcation being substantially equal.

EDWARD Brn'rz. 

